Currently a lithium ion battery has an extensive application in such electronic devices as mobile telephones, portable computers, and portable audio-visual equipment. However, price of its anode material, lithium cobalt oxide (LiCoO2), is going up continuously because of resource problems, which limits development of the lithium ion battery. Therefore, people have been working hard to look for a suitable substitute material. The material recently studied most is such composite anode materials as cobalt nickel manganese. The most widely used method reported in literature is a codeposition method. According to this method, prepare a metal salt solution according to a certain proportion; add such additives as ammonia water to control crystallization velocity of a hydroxide; and then react with an alkali to produce a deposit. In accordance with this method, add ammonia water into a base solution; after the salt solution is dripped into the base solution, first such metallic ions as Ni2+ and Co2+ have a complexation with ammonia (NH3) to produce a complex ion of X(NH3) n2+(n=1˜6, X=Ni, Co), concentration of the metallic ion being lowered; then amount of Ni2+ and Co2+ is dramatically reduced due to their reaction with OH− to produce a hydroxide deposit; and then M(NH3)n2+ releases the complex metallic ions to keep a certain concentration of the metallic ions in the solution. However, this method has the following shortcoming: After the salt solution is added into the base solution, ammonia (NH3) and OH− coexist with the metallic ions, resulting in a competitive behavior; and it is very difficult for ammonia (NH3) to control crystallization due to the fact that it is easier for OH− than NH3 to react with such ions as Ni2+ and Co2+, which makes the intermediate particles have an irregular microstructure and a wider size distribution.
Umicore, Belgium thinks that the material with a bigger particle size has a poorer cycling performance. According to the research done by Guoliang Wu et al., particle size distribution of the material has a remarkable influence on the discharge capacity, especially on the charge-discharge cycling performance; and the wider the particle size distribution, the poorer the cycling performance. The reason is that, the material with a wider particle size distribution will have a poor porosity, which affects its capillarity with an electrolyte and thus makes the impedance show higher; and when the battery is charged to an extreme potential, Li+ on surface of a big particle will deintercalate excessively, which will damage its layered structure and is to the disadvantage of the cycling performance.